During its 6,300-km course from the Tibetan Plateau to the ocean, the Yangtze River is joined by two large lakes: Dongting Lake and Poyang Lake. We explain why these lakes exist. Deglaciation forced the ocean adjacent to the Yangtze mouth to rise ∼120 m. This forced a wave of rising water surface elevation and concomitant bed aggradation upstream. While aggradation attenuated upstream, the low bed slope of the Middle-Lower Yangtze River (∼2 × 10 −5 near Wuhan) made it susceptible to sea level rise. The main stem, sourced at 5,054 m above sea level, had a substantial sediment load to “fight” against water surface level rise by means of bed aggradation. The tributaries of the Middle-Lower Yangtze have reliefs of approximately hundreds of meters, and did not have enough sediment supply to fill the tributary accommodation space created by main-stem aggradation. We show that the resulting tributary blockage likely gave rise to the lakes. We justify this using field data and numerical modeling, and derive a dimensionless number capturing the critical rate of water surface rise for blockage versus nonblockage.

中文翻译：

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长江鄱阳湖和洞庭湖：支流湖被主干加积阻塞

在从青藏高原到海洋的 6300 公里长江流域中，有两个大湖：洞庭湖和鄱阳湖。我们解释了为什么这些湖泊存在。冰川消退迫使长江口附近的海洋上升约 120 m。这迫使上游水面升高和伴随的河床加积一波上升。在上游加积减弱的同时，长江中下游低床坡度（~2×10−5武汉附近）使其容易受到海平面上升的影响。主干源位于海拔 5,054 米处，具有大量沉积物负荷，可以通过河床加积来“对抗”水位上升。长江中下游支流地势起伏约数百米，泥沙供应不足以填满主干加积形成的支流可容空间。我们表明，由此产生的支流堵塞可能导致了湖泊。我们使用现场数据和数值建模来证明这一点，并推导出一个无量纲数，用于捕捉堵塞与非堵塞的水面上升临界速率。